The invention relates to meat processing. More particularly, the invention relates to an apparatus and process for treating meat products with ammonia.
Meat products are subject to contamination with certain dangerous microorganisms such as various strains of E. Coli bacteria, for example. Although with careful handling and processing it is possible to reduce the risk of contamination, there is always the possibility that undesirable microorganisms will come into contact with a meat product in the course of processing. Once a meat product is contaminated with a dangerous microorganism, the microorganism may, depending upon handling and conditions, multiply and reach dangerous levels in the meat product. Also, the dangerous microorganisms present on the contaminated meat product may be distributed to surrounding meat products in the course of further processing and storage.
Numerous techniques have been developed for killing or otherwise eliminating dangerous microorganisms which may be found in meat products. Other techniques focus on controlling the growth of microorganisms in the meat products. For example, heat sterilization may be used to kill microorganisms in meat products. However, heat sterilization affects the nature of the meat product. Also, the cooked or partially cooked meat product may again support rapid growth of dangerous microorganisms which may come in contact with the meat product after heat sterilization. In addition to heat sterilization, chemical preservatives may be added to control the growth of microorganisms in cooked, uncooked, or partially cooked meat products. Another sterilization technique includes bombarding the meat product with various types of electromagnetic radiation to kill microorganisms which may be present in the meat product. All of the above-described microorganism control or sterilization techniques are associated with undesirable side effects or other problems which have prevented their acceptance throughout the meat processing industry.
U.S. Pat. No. 5,871,795, to the inventor of the present invention, discloses a method and apparatus for modifying the pH of a meat using ammonia. The application of ammonia according to that patent reduces the levels of certain dangerous microorganisms immediately after treatment and also controls the growth of dangerous microorganisms in the meat product as it is stored after treatment. In U.S. Pat. No. 5,871,795 the meat is compressed in contact with ammonia gas to an operating pressure for a short period of time. This operating pressure comprises a pressure greater than the vapor pressure of ammonia at the temperature of the meat product being processed. The purpose of applying the ammonia gas under pressure is to quickly increase the pH of the foodstuff without having to expose the meat product to ammonia for an extended period of time. It has been found that extended exposure to ammonia may adversely affect certain properties of a meat product. In particular, exposing a meat product to ammonia for an extended period of time may cause the meat product to produce an undesirable ammonia odor after treatment.
Prior related U.S. patent application Ser. No. 09/286,699, now U.S. Pat. No. 6,142,067, discloses an apparatus and method for treating an ammoniated meat. The object of that invention is to prevent the ammonia previously added to the meat from affecting the taste or smell of the meat product, while raising the pH of the meat product consistently throughout the material. This prior treatment system requires comminuting the meat and is thus suited only for products such as ground meats and other comminuted meat products.
There remains a need for an arrangement for applying ammonia to meats, particular whole or noncomminuted meats, so as to produce the desired pH change in the meat product without leaving the meat product with an undesirable ammonia odor or undesirable flavor.
It is an object of the invention to provide a method and apparatus for treating meat products with ammonia without leaving the meat products with an undesirable ammonia odor or an undesirable flavor.
The treatment method according to the invention includes first applying ammonia to a meat product to produce an ammoniated meat product. The method then includes containing the ammoniated meat product in a treatment gas atmosphere which is either substantially free of ammonia gas or has a low ammonia gas content. A treatment vessel is used to contain the ammoniated meat product in the desired treatment gas atmosphere. Once the ammoniated meat product is contained in the appropriate treatment gas atmosphere, the method includes increasing the pressure of the treatment gas atmosphere to an operating pressure preferably greater than the vapor pressure of ammonia at the temperature of the ammoniated meat product being treated. This increased pressure is held on the ammoniated meat product for an operating period effective to reduce the amount of ammonia gas which escapes from the meat product after the product is placed again under atmospheric conditions, thus leaving the treated meat product with no significant ammonia odor.
It is important to note that the present ammonia treatment does not require any grinding or comminution of the meat product. The invention is therefore well suited for chunks or large cuts of meat and meat products. As used in this disclosure, the term xe2x80x9cwhole meat productxe2x80x9d will be used to describe a chunk or large cut of either whole-muscle or formed meat product. It will be appreciated that a xe2x80x9cwhole meat productxe2x80x9d under this definition may itself be formed from comminuted material. For example, a whole meat product under this definition may comprise a patty of ground or other comminuted meat, or may comprise a sausage or frankfurter made from a comminuted meat batter. Also, the phrase xe2x80x9cwhole meat productxe2x80x9d is not intended to imply that the meat product includes only meat components. Rather, a whole meat product may be made up of meat components along with non meat additives or fillers.
Ammonia may be applied to the meat product in any suitable manner. For example, the meat product may be exposed to ammonia gas or sprayed with a solution of ammonia in water. The ammonia may be applied in a separate ammonia application device or vessel, or may be applied in a single vessel also used in applying the treatment gas pressure to the meat product. Regardless of how the ammonia is applied, the treatment gas atmosphere maintained during the pressurization step according to the invention should comprise an atmosphere or environment having a low ammonia gas content. That is, the ammonia gas content in the treatment gas atmosphere should be sufficiently low that the meat product will not become over-ammoniated during application of the treatment gas. The meat product would be over-ammoniated if it is left with an undesirable odor or taste after the treatment gas application. In order to prevent the meat product from becoming over-ammoniated, the partial pressure of ammonia gas in the treatment gas atmosphere of the operating pressure preferably remains below the vapor pressure of ammonia at the temperature of the meat product being treated, while the total pressure of the treatment gas atmosphere may be a pressure above the vapor pressure of ammonia at the temperature of the meat product being treated. A treatment gas atmosphere in which the ammonia content is sufficiently low to prevent the meat from becoming over-ammoniated during the treatment gas pressurization step will be referred to in this disclosure and the following claims as a substantially ammonia free atmosphere. A gas having an ammonia partial pressure below the vapor pressure of ammonia at the temperature of the meat product being treated is an example of a substantially ammonia free atmosphere.
Since pressurizing the ammoniated meat product in an atmosphere containing excessive ammonia gas could apply excessive ammonia to the meat product, the invention may include the step of removing excess ammonia gas from the treatment vessel prior to applying the treatment gas operating pressure. The ammonia gas to be removed may be left over from the ammonia application step in the treatment vessel or may be ammonia released from the meat product as it is being transferred to the treatment vessel. In any event, the step of removing ammonia gas from the treatment vessel may include injecting a purge gas into the treatment vessel to purge at least a portion of any ammonia gas from the treatment vessel through a suitable gas outlet opening in the vessel. This purging step may be performed either with or without first applying a vacuum within the treatment vessel. The purge gas may be substantially any gas suitable for use with the ammoniated meat product. Preferably, the gas used to purge the treatment vessel of excess ammonia may comprise the treatment gas under which the ammoniated meat product is pressurized to the operating pressure.
The operating pressure may be applied in any suitable fashion within the scope of the invention. For example, the treatment gas pressurization step may be performed by releasing pressurized treatment gas into the treatment vessel from a treatment gas supply. Alternatively, treatment gas may be compressed in the treatment vessel using a suitable piston and cylinder arrangement associated with the treatment vessel.
The treatment gas may be made up primarily of an inert gas or any suitable gas which does not chemically react with ammonia. Alternatively, the treatment gas may be or may include a neutralizing component which neutralizes ammonia or ammonium hydroxide. Carbon dioxide gas is an example of such a neutralizing gas component which may be included in the treatment gas. As yet another alternative, the treatment method may include a separate neutralization step between the ammonia application step and the treatment gas pressurization step. This neutralization step may comprise placing the ammoniated meat in a neutralizing gas atmosphere to neutralize at least a portion of the ammonia or ammonium hydroxide in the vessel or on the meat after the ammonia application step.
The invention may be used to provide a desired pH change in a meat product without having to comminute or grind the product. Most importantly, any significant ammonia odor is eliminated from the resulting ammoniated meat product.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.